Use the motion of the two planets to determine the value of k in Kepler's Third Law, P² = k a³, where P is the orbital period and a is the average distance from the star. Fortunately, all objects here orbit in perfect circles - not an entirely realistic scenario, but much easier to deal with. The orbital period is given in years in the lower right corner, while the scale shown is the distance from the star given in AUs s (Astronomical Units). If you click on the orbital map it will provide the distance of the object in AU. Be sure to click on the center of the object to show the distance from the star.

Use the following keys to control the simulation,

• M - to start and restart the simulation (Press this first!)
• X - to stop the motion
• R - to reset the simulation to the starting location
• N - create two completely different planets

All of the planets are generated randomly, however they all obey Kepler's Laws and all orbit the same mass star - whose mass is not equal to that of the Sun.

If you are having problems with this simulation, you can also get the data using this link.